Drought-weary California, heading into a long, hot summer of water shortages and extreme fire risk, received some potentially good news Thursday, as federal scientists announced there is now a 4-in-5 chance of El Ni?o conditions developing by the end of the year.

"The trend continues. We are now even more bullish that an El Ni?o is impending," said Michelle L'Heureux, a meteorologist with the National Oceanic and Atmospheric Administration's Climate Prediction Center in College Park, Md.

El Ni?o events — which occur when sea surface temperatures in the Pacific Ocean at the equator become warmer than normal, affecting the jet stream — can lead to wetter winters in California.

Citing a huge mass of warm water that continues to move east toward South America, NOAA increased its probability for El Ni?o developing next winter to 78 percent, up from 66 percent last month, and 36 percent in November.

But there's no guarantee California's persistent drought will be over in six months. Generally speaking, the warmer the ocean water, the increased likelihood of heavy rainfall during El Ni?o years. During mild El Ni?o years, when the ocean water is only slightly warmer than historic averages, there are just as many drier-than-average years as soaking ones.

"There are all kinds of El Ni?os: small, medium, large and Godzilla," said Bill Patzert, a research scientist and oceanographer at NASA's Jet Propulsion Laboratory in Pasadena.

"I don't see the Godzilla. But I'll give it another couple of months," he said. "This still could be El Fizzle. I don't want to recommend that you invest any of your retirement in the umbrella market yet."

California may still receive a few small showers in the weeks ahead. But based on historic patterns, in which less than 5 percent of the state's annual rainfall occurs after May 1, this year's winter rainy season is over. And the verdict isn't good.

Despite some healthy downpours in March, on Thursday the Sierra Nevada snowpack, a key source of water for farms and cities, was 13 percent of the historic average for this date. Major reservoirs, hamstrung by 2013 being the driest year in recorded California history, are mostly at about half of their historic average for the beginning of summer.

Leaders at California water districts are privately hoping that the El Ni?o shaping up in the Pacific Ocean now will save them from what will be dire circumstances with widespread water rationing next year if the upcoming winter is unusually dry again, creating a fourth dry year in a row.

NOAA scientists, who glean information from buoys, satellites and super computers, say that with each passing month, they will know more about how strong the emerging El Ni?o will be. Currently, computer models run by many of the world's top weather agencies estimate that sea surface temperatures will range from about 1 to 3 degrees Fahrenheit warmer than normal by next fall.

The last major, soaking El Ni?o event, in 1997, saw surface temperatures 5 degrees warmer than normal at some times. That led to the second wettest year in Northern California history with major flooding and landslides, and 35 counties being declared disaster areas.

California water managers say the best case would be a fairly strong El Ni?o event that brings rainfall next winter to about 50 percent more than average , but not much more than that.

"We want to see sustained, above-normal precipitation and above-normal snowpack, but not so over-the-top that you end up with major flooding," said Michael Anderson, the state climatologist with the California Department of Water Resources.

"There's a lot of interest in this. People are hopeful," he said. "You hope for the best. But we don't know how it is going to turn out yet. We have to temper our enthusiasm."